Carbon dioxide recovery apparatus and carbon dioxide recovery method

ABSTRACT

In one embodiment, a carbon dioxide recovery apparatus includes a heat exchanger which heats a first rich liquid, a flow divider which divides the first rich liquid heated by the heat exchanger into a second rich liquid and a third rich liquid, a first release device which heats the second rich liquid and discharges a first semi-lean liquid, a second release device which heats the third rich liquid and discharges a second semi-lean liquid, and a regeneration tower which heats the first and second semi-lean liquids to generate a lean liquid. The first release device heats the second rich liquid, using the lean liquid. The second release device heats the third rich liquid, using a carbon dioxide-containing steam discharged at the regeneration tower. The heat exchanger heats the first rich liquid, using the lean liquid which has passed through the first release device.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims benefit of priority from theJapanese Patent Application No. 2012-49597, filed on Mar. 6, 2012, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a carbon dioxiderecovery apparatus and a carbon dioxide recovery method.

BACKGROUND

Recently, regarding recovery of carbon dioxide, carbon dioxide captureand storage techniques have attracted attention as effectivecountermeasures to the problem of global warming which is concerned on aglobal scale. Particularly, there has been considered a method forrecovering carbon dioxide with an aqueous solution for a thermal powerstation and a process emission gas.

As such a carbon dioxide recovery apparatus, there has been known onewhich is provided with: an absorption tower which causes a carbondioxide-containing gas to be absorbed into an absorbing liquid andgenerates a rich liquid; a desorption tower which heats the rich liquiddischarged from the absorption tower to desorb carbon dioxide with steamand, thus, to separate carbon dioxide-containing steam, and returns agenerated lean liquid to the absorption tower; a first heat exchangerthrough which the lean liquid supplied from the desorption tower to theabsorption tower passes; a second heat exchanger through which thecarbon dioxide-containing steam separated in the desorption towerpasses; and a flow divider which distributes the rich liquid dischargedfrom the absorption tower to the first and second heat exchangers. Inthis carbon dioxide recovery apparatus, after the rich liquidsintroduced into the first and second heat exchangers exchange the heatwith the lean liquid and the carbon dioxide-containing steam,respectively, the rich liquid is supplied to the desorption tower.

In the above conventional carbon dioxide recovery apparatus, thermalenergy of the carbon dioxide-containing steam separated in thedesorption tower can be recovered in the second heat exchanger by thedistributed rich liquid. However, the flow rate of the rich liquidpassing through the first heat exchanger is reduced to facilitateincrease in temperature, and consequently, a temperature difference fromthe lean liquid as a high-temperature side fluid is reduced, wherebythere is a problem that an amount of thermal energy recovered from thelean liquid at this site is reduced more than in a case where the richliquid is not divided. This tendency becomes more notable when theperformance of the first heat exchanger is improved by measures such asincreasing a heat transfer area to reduce the amount of steamconsumption in the carbon dioxide recovery apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of a carbon dioxide recoveryapparatus according to a first embodiment;

FIG. 2 is a graph showing a relationship between temperatures of a richliquid and a lean liquid and a heat exchange duty in the firstembodiment;

FIG. 3 is a schematic configuration diagram of a carbon dioxide recoveryapparatus according to a comparative example;

FIG. 4 is a graph showing a relationship between temperatures of a richliquid and a lean liquid and a heat exchange duty in the comparativeexample;

FIG. 5 is a schematic configuration diagram of a carbon dioxide recoveryapparatus according to a second embodiment;

FIG. 6 is a graph showing a performance curve of a carbon dioxiderecovery apparatus according to a second embodiment;

FIG. 7 is a schematic configuration diagram of a carbon dioxide recoveryapparatus according to a third embodiment;

FIG. 8 is a schematic configuration diagram of a carbon dioxide recoveryapparatus according to a fourth embodiment;

FIG. 9 is a schematic configuration diagram of a carbon dioxide recoveryapparatus according to a fifth embodiment; and

FIG. 10 is a schematic configuration diagram of a carbon dioxiderecovery apparatus according to a sixth embodiment.

DETAILED DESCRIPTION

In one embodiment, a carbon dioxide recovery apparatus includes anabsorption tower which generates a first rich liquid, a heat exchangerwhich heats the first rich liquid, a flow divider which divides thefirst rich liquid heated by the heat exchanger into a second rich liquidand a third rich liquid, a first release device which heats the secondrich liquid and discharges a first semi-lean liquid, a second releasedevice which heats the third rich liquid and discharges a secondsemi-lean liquid, and a regeneration tower which heats the first andsecond semi-lean liquids to generate a lean liquid. The first releasedevice heats the second rich liquid, using the lean liquid. The secondrelease device heats the third rich liquid, using a carbondioxide-containing steam discharged at the regeneration tower.

The heat exchanger heats the first rich liquid, using the lean liquidwhich has passed through the first release device.

Embodiments will now be explained with reference to the accompanyingdrawings.

(First Embodiment) FIG. 1 shows a schematic configuration of a carbondioxide recovery apparatus according to a first embodiment. A carbondioxide recovery apparatus 1 includes, as main components, an absorptiontower 101, a regeneration tower 102, carbon dioxide release devices 103and 104, coolers 105 and 106, a reboiler 108, a heat exchanger 109, anda gas-liquid separator 132.

The carbon dioxide recovery apparatus 1 is further provided with pumps201 and 202, a flow divider 107, and a converging device 110.

In the absorption tower 101, a carbon dioxide-containing gas 111 isintroduced to be in contact with an absorbing liquid for absorbingcarbon dioxide, and, thus, to generate a rich liquid 301 having absorbedcarbon dioxide.

The absorption tower 101 includes a countercurrent gas-liquid contactdevice, for example. In the absorption tower 101, the carbon dioxidecontaining gas 111 supplied from a lower portion of the absorption tower101 is in gas-liquid contact with a lean liquid 319 flowing down from anupper portion of the absorption tower 101.

Although the carbon dioxide containing gas 111 supplied to theabsorption tower 101 is not particularly limited, the carbondioxide-containing gas may be a combustion exhaust gas, a processemission gas, or the like and may be introduced after a coolingtreatment, as necessary.

The absorbing liquid is not particularly limited, and an amine-basedaqueous solution, such as monoethanolamine (MEA) and diethanolamine(DEA) may be used. A gas 112 from which carbon dioxide has been removedin the absorption tower 101 is discharged from the upper portion of theabsorption tower 101.

The rich liquid 301 discharged from the absorption tower 101 isintroduced into the heat exchanger 109 through the pump 201, and isheated to a desired temperature by the lean liquid 319.

The rich liquid 301 heated in the heat exchanger 109 is given to theflow divider 107 and then divided into rich liquids 302 and 303 with adesired flow ratio.

The rich liquids 302 and 303 are heated in the carbon dioxide releasedevices 103 and 104, respectively. Some carbon dioxide is released withsteam and discharged as gas-liquid two-phase semi-lean liquids 320 and306, in which a portion of the carbon dioxide has been removed from theliquid.

In the carbon dioxide release device 103 which is a first carbon dioxiderelease device, the lean liquid 319 supplied from the regeneration tower102 to the absorption tower 101 is a heat source.

In the carbon dioxide release device 104 which is a second carbondioxide release device, the carbon dioxide-containing steam 310separated in the regeneration tower 102 to be described later is a heatsource.

As described above, the rich liquids 302 and 303 supplied respectivelyto the carbon dioxide release devices 103 and 104 are heated by heatexchange with the lean liquid 319 and the carbon dioxide-containingsteam 310, and some carbon dioxide is released with steam.

In the carbon dioxide release device 104, a portion of water vapor iscondensed, and the discharged carbon dioxide-containing steam 311 issupplied to the cooler 105 to be cooled by a coolant such as cold watersupplied externally and, thus, to be discharged to the gas-liquidseparator 132. In the gas-liquid separator 132, the discharged carbondioxide-containing steam 311 is separated into carbon dioxide 315 andcondensate water 314 and then discharged.

The semi-lean liquids 320 and 306 in which a portion of the carbondioxide is released converge in the converging device 110 and aresupplied to the regeneration tower 102.

The regeneration tower 102 is provided with a packed bed 102 a, and thesemi-lean liquid supplied from the converging device 110 is heated,whereby the majority of carbon dioxide is released with steam anddischarged as the carbon dioxide-containing steam 310 from an upperportion of the regeneration tower 102. The lean liquid 319, in which themajority of carbon dioxide has been removed, is returned to theabsorption tower 101.

The regeneration tower 102 is a countercurrent gas-liquid contactdevice, for example, and a stored liquid is heated by heat exchange withhigh-temperature steam as externally-supplied heat in the reboiler 108.

In a path through which the lean liquid 319 is supplied from theregeneration tower 102 to the absorption tower 101, the carbon dioxiderelease device 103, the heat exchanger 109, and the cooler 106 areprovided in sequence. The lean liquid 319 discharged from theregeneration tower 102 is supplied to the carbon dioxide release device103 through the pump 202. The lean liquid 319 exchanges the heat withthe rich liquid 302 in the carbon dioxide release device 103, exchangesthe heat with the rich liquid 301 in the heat exchanger 109, and iscooled by a coolant such as cold water supplied externally in the cooler106. Thereafter, the lean liquid 319 is returned to the absorption tower101.

According to the carbon dioxide recovery apparatus 1 having the aboveconstitution, the following operations and effects are obtained.

First, in the absorption tower 101, a carbon dioxide absorption processin which the carbon dioxide-containing gas 111 is absorbed in theabsorbing liquid to generate the rich liquid 301 is performed.

The rich liquid 301 discharged from the absorption tower 101 is heated(preheated) by the lean liquid 319 in the heat exchanger 109 and thendivided. The divided liquids become the gas-liquid two-phase semi-leanliquids 320 and 306 in which some carbon dioxide is released in thecarbon dioxide release devices 103 and 104, respectively. The semi-leanliquids 320 and 306 converged by the converging device 110 are suppliedto the regeneration tower 102, and carbon dioxide heated by the reboiler108 and remaining in a liquid phase is released to move upward as carbondioxide-containing steam.

While the carbon dioxide-containing steam 310 is discharged from theupper portion of the regeneration tower 102, the lean liquid 319 isreturned to the absorption tower 101.

As described above, a regeneration process in which the rich liquid 301having absorbed carbon dioxide becomes the lean liquid 319 is performed.

The lean liquid 319 discharged from the regeneration tower 102 issupplied to the absorption tower 101 through the carbon dioxide releasedevice 103, the heat exchanger 109, and the cooler 106. The carbondioxide-containing steam 310 separated in the regeneration tower 102 issupplied to the gas-liquid separator 132 through the carbon dioxiderelease device 104 and the cooler 105.

The rich liquid 301 discharged from the absorption tower 101 ispreheated by the lean liquid 319 in the heat exchanger 109 and thendivided by the flow divider 107. The divided liquids are introduced intothe carbon dioxide release devices 103 and 104, exchange the heat withthe lean liquid 319 and the carbon dioxide-containing steam 310,respectively, and are then supplied to the regeneration tower 102.

The temperatures of the semi-lean liquids 320 and 306 introduced intothe regeneration tower 102 can be satisfactorily increased by using thetwo carbon dioxide release devices 103 and 104 and, at the same time, aportion of carbon dioxide is released. The release of carbon dioxide andwater evaporation associated with the release are endothermic reactions.Since a temperature difference between the rich liquid and the leanliquid in the carbon dioxide release device 103 or a temperaturedifference between the rich liquid and the carbon dioxide-containingsteam in the carbon dioxide release device 104 can be increased incomparison with the case in which the rich liquid does not change itsphase, heat recovery from the lean liquid and the carbon dioxidecontaining steam with the use of the rich liquid can be more effectivelyperformed.

Since the rich liquid 301 before being divided is previously heatedwhile the temperature difference between the rich liquid 301 and thelean liquid is secured in the heat exchanger 109, it is possible toprevent the temperatures of the rich liquid and the lean liquid frombeing excessively close to each other (the temperature difference frombeing extremely reduced) until the release of carbon dioxide and thewater evaporation occur in the carbon dioxide release device 103, andreduction of efficiency of heat exchange can be suppressed.

FIG. 2 is a graph showing a relationship between the temperatures of therich liquid and the lean liquid and a heat exchange duty when the heatexchanger 109 and the carbon dioxide release device 103 are consideredtogether. In FIG. 2, the rich liquid is shown by a solid line, and thelean liquid is shown by a dashed line. As can be seen from FIG. 2, oncethe release of carbon dioxide and the water evaporation associated withthe release, which are endothermic reactions, start upon a temperatureincrease, the temperature difference between the rich liquid and thelean liquid gradually increases.

(Comparative example) FIG. 3 shows a schematic configuration of a carbondioxide recovery apparatus 10 according to a comparative example. Thecarbon dioxide recovery apparatus 10 is different from the carbondioxide recovery apparatus 1 according to the first embodiment shown inFIG. 1 in that the heat exchanger 109 is not provided. FIG. 4 is a graphshowing a relationship between temperatures of a rich liquid and a leanliquid in a carbon dioxide release device 103 of the carbon dioxiderecovery apparatus 10 and a heat exchange duty. In FIG. 4, the richliquid is shown by a solid line, and the lean liquid is shown by adashed line.

As can be seen from FIG. 4, in the carbon dioxide recovery apparatus 10,the temperatures of the rich liquid and the lean liquid are excessivelyclose to each other (the temperature difference is extremely reduced)until the release of carbon dioxide and the water evaporation occur.Until the temperature of the rich liquid 302 flowing in the carbondioxide release device 103 is increased by heat exchange to releasecarbon dioxide, the flow rate of the rich liquid is lower in comparisonwith the case in which the rich liquid is not divided. Therefore, thetemperature of the rich liquid easily increases, and the temperaturedifference between the rich liquid and the lean liquid which is ahigh-temperature side fluid is reduced, whereby the efficiency of theheat exchange is more reduced than the case in which the rich liquid isnot divided.

Meanwhile, according to the first embodiment, the temperature of therich liquid is previously increased while the temperature differencebetween the rich liquid and the lean liquid is secured in the heatexchanger 109, whereby it is possible to prevent the temperatures of therich liquid and the lean liquid from getting close to each other in thecarbon dioxide release device 103. Comparing FIG. 2 to FIG. 4, the heatexchange amount in the first embodiment is larger by about 5% than thatin the comparative example.

As described above, according to the first embodiment, the heatrecovery, using the rich liquid, from the lean liquid and the carbondioxide-containing steam can be effectively performed.

In this embodiment, although the heat exchanger 109, the flow divider107, and the carbon dioxide release device 103 are separately installed,all the components may be integrated as a single carbon dioxide releasedevice, and a flow divider may be provided in the carbon dioxide releasedevice.

As shown in FIG. 1, in the first embodiment, the condensate water 314separated by the gas-liquid separator 132 is returned to theregeneration tower 102. However, the condensate water 314 may bereturned to the absorption tower 101 or may be utilized in otherapplications.

(Second Embodiment) FIG. 5 shows a schematic configuration of a carbondioxide recovery apparatus 2 according to a second embodiment. Thecarbon dioxide recovery apparatus 2 is different from the carbon dioxiderecovery apparatus 1 according to the first embodiment shown in FIG. 1in that the carbon dioxide recovery apparatus 2 is provided with a flowdivider 120 and a converging device 121. Since other constitutions andoperations are similar to those of the first embodiment, descriptionthereof will not be repeated.

In this embodiment, a rich liquid 301 is divided into rich liquids 301 aand 301 b in the flow divider 120 to the extent that the temperatures ofa rich liquid and a lean liquid are not too close to each other in aheat exchanger 109. The rich liquid 301 a is supplied to the heatexchanger 109, and the rich liquid 301 b is supplied to the convergingdevice 121. In the converging device 121, the rich liquid 301 b and therich liquid 303 from a flow divider 107 are mixed and then supplied to acarbon dioxide release device 104. Consequently, since the temperatureof the rich liquid at the entrance of the carbon dioxide release device104 is lower in comparison with the first embodiment, the heat exchangeamount in the carbon dioxide release device 104 can be increased.

FIG. 6 shows a performance curve of the carbon dioxide recoveryapparatus 2. The total flow rate of the rich liquid 301 b and the richliquid 303 is fixed at 10% of the flow rate of the rich liquid 301discharged from an absorption tower 101.

The horizontal axis of the graph of FIG. 6 is the flow rate ratio of therich liquid 303 to the rich liquid 301. The flow rate ratio of 0%corresponds to the absence of the rich liquid 303, that is, the absenceof the flow divider 107. The flow rate ratio of 10% corresponds to theabsence of the rich liquid 301 b, and in this case, the carbon dioxiderecovery apparatus 2 is similar to the carbon dioxide recovery apparatus1 according to the first embodiment shown in FIG. 1.

In FIG. 6, a plot of black circles represents CO₂ capture ratio, and aplot of triangles represents CO₂ recovery energy. The CO₂ capture ratiois the flow rate ratio of carbon dioxide 315 to carbon dioxide in acarbon dioxide-containing gas 111 supplied to the absorption tower 101.The CO₂ recovery energy is energy of steam which is required forrecovering 1 ton of carbon dioxide and is consumed in a reboiler 108.

FIG. 6 shows that when the total flow rate of the rich liquid 301 b andthe rich liquid 303 is fixed at 10% of the flow rate of the rich liquid301, the flow rate of the rich liquid 303 to the rich liquid 301 is setto approximately 5% (the flow rates of the rich liquid 301 b and therich liquid 303 are made comparable to each other), so that the CO₂recovery energy is reduced, and, at the same time, the CO₂ capture ratiocan be increased.

(Third Embodiment) FIG. 7 shows a schematic configuration of a carbondioxide recovery apparatus 4 according to a third embodiment. The carbondioxide recovery apparatus 4 is different from the carbon dioxiderecovery apparatus 3 according to the second embodiment shown in FIG. 5in that a carbon dioxide release device 122 which is a third carbondioxide release device is further provided.

In this embodiment, carbon dioxide-containing steam 310 discharged froma regeneration tower 102 first exchanges the heat with a rich liquid 303in a carbon dioxide release device 104. Then, the carbondioxide-containing steam 310, having exchanged the heat with the richliquid 303, exchanges the heat with a rich liquid 301 b in the carbondioxide release device 122. Semi-lean liquids discharged from the carbondioxide release devices 103, 104, and 122 are mixed in a convergingdevice 110 and supplied to a regeneration tower 102.

Namely, the rich liquid 303 at a higher temperature than the rich liquid301 b exchanges the heat with the carbon dioxide-containing steam 310prior to the rich liquid 301 b. According to the above constitution,since a temperature difference between a high-temperature side fluid(carbon dioxide-containing steam 310) and a low-temperature side fluid(rich liquids 303 and 301 b) can be kept large, the efficiency of theheat exchange can be enhanced.

Since other constitutions and operations are similar to those of thesecond embodiment, description thereof will not be repeated.

(Fourth Embodiment) FIG. 8 shows a schematic configuration of a carbondioxide recovery apparatus 5 according to a fourth embodiment. Thecarbon dioxide recovery apparatus 5 is different from the carbon dioxiderecovery apparatus 1 according to the first embodiment shown in FIG. 1in that the carbon dioxide release device 104 is not provided outsidethe regeneration tower 102. Thus, in this embodiment, a rich liquid 303divided from a flow divider 107 is directly supplied to the regenerationtower 102. In this embodiment, a converging device 110 is not provided.

As shown in FIG. 8, the heat exchange between a semi-lean liquid 320 andthe rich liquid 303 and carbon dioxide-containing steam is performed inthe regeneration tower 102. Although, in the first embodiment, theregeneration tower 102 is provided with only the packed bed 102 a, inthis embodiment a packed bed 102 b is provided above the packed bed 102a.

The rich liquid 303 is supplied from above the upper packed bed 102 b topass through the packed bed 102 b, and, thus, to move downward. Thesemi-lean liquid 320 is supplied between the packed beds 102 a and 102 bto pass through the lower packed bed 102 a, and, thus, to move downward.Carbon dioxide-containing steam passes upward through the packed beds102 a and 102 b, and heat exchange is performed. Namely, in thisembodiment, instead of the carbon dioxide release device 104, the packedbed 102 b having a function equivalent to that of the carbon dioxiderelease device 104 is provided as a carbon dioxide release device in theregeneration tower 102.

Since the carbon dioxide-containing steam contained in the semi-leanliquid 320 moves upward after being introduced into the regenerationtower 102, the carbon dioxide-containing steam acts as a heating mediumfor the rich liquid 303.

The carbon dioxide-containing steam 310 discharged from an upper portionof the regeneration tower 102 is directly supplied to a cooler 105 to becooled and, then, is supplied to a gas-liquid separator 132.

As described above, according to this embodiment, since the carbondioxide release device 104 and the converging device 110 are notrequired to be provided, the number of necessary pipes is smaller thanthat in the first embodiment, and cost can be reduced.

(Fifth Embodiment) FIG. 9 shows a schematic configuration of a carbondioxide recovery apparatus 6 according to a fifth embodiment. The carbondioxide recovery apparatus 6 is different from the carbon dioxiderecovery apparatus 5 according to the fourth embodiment shown in FIG. 8in that the carbon dioxide recovery apparatus 6 is provided with a flowdivider 120 and a converging device 121. Since other constitutions andoperations are similar to those of the fourth embodiment, descriptionthereof will not be repeated.

In this embodiment, a rich liquid 301 is divided into rich liquids 301 aand 301 b in the flow divider 120 to the extent that the temperatures ofa rich liquid and a lean liquid are not too close to each other in aheat exchanger 109, the rich liquid 301 a is supplied to the heatexchanger 109, and the rich liquid 301 b is supplied to the convergingdevice 121. In the converging device 121, the rich liquid 301 b and therich liquid 303 from a flow divider 107 are mixed and then supplied to aregeneration tower 102. Consequently, since the temperature of the richliquid at the inlet of the regeneration tower 102 is lower in comparisonwith the fifth embodiment, the heat exchange amount in the regenerationtower 102 can be increased.

(Sixth Embodiment) FIG. 10 shows a schematic configuration of a carbondioxide recovery apparatus 7 according to a sixth embodiment. The carbondioxide recovery apparatus 7 is different from the carbon dioxiderecovery apparatus 6 according to the fifth embodiment shown in FIG. 9in that the converging device 121 is not provided.

In this embodiment, a packed bed 102 c is provided above a packed bed102 b in a regeneration tower 102. A rich liquid 301 b divided in a flowdivider 120 is supplied from above the upper packed bed 102 c. A richliquid 303 divided in a flow divider 107 is supplied between the upperpacked bed 102 c and the middle packed bed 102 b.

In this embodiment, carbon dioxide-containing steam having exchanged theheat with the rich liquid 303 exchanges the heat with the rich liquid301 b. Namely, the rich liquid 303 at a higher temperature than the richliquid 301 b exchanges the heat with the carbon dioxide-containing steamprior to the rich liquid 301 b. According to the above constitution,since a temperature difference between a high-temperature side fluid(carbon dioxide-containing steam) and a low-temperature side fluid (richliquids 303 and 301 b) can be kept large, the efficiency of the heatexchange can be further enhanced.

Since other constitutions and operations are similar to those of thefifth embodiment, description thereof will not be repeated.

According to at least one of the embodiments described above, the heatrecovery, using the rich liquid, from the lean liquid and the carbondioxide-containing steam can be effectively performed.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made without departing from the spiritof the inventions. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fall within thescope and spirit of the inventions.

What is claimed is:
 1. A carbon dioxide recovery apparatus comprising:an absorption tower which introduces therein carbon dioxide-containinggas and brings the carbon dioxide-containing gas into contact with anabsorbing liquid for absorbing carbon dioxide to generate a first richliquid having absorbed the carbon dioxide, and, thus, to discharge thefirst rich liquid; a heat exchanger which heats the first rich liquid; aflow divider which divides the first rich liquid heated by the heatexchanger into a second rich liquid and a third rich liquid; a firstcarbon dioxide release device which heats the second rich liquid andthereby discharges a first semi-lean liquid in which carbondioxide-containing steam is released; a second carbon dioxide releasedevice which heats the third rich liquid and thereby discharges a secondsemi-lean liquid in which carbon dioxide-containing steam is released;and a regeneration tower which heats the first semi-lean liquid and thesecond semi-lean liquid to release remaining carbon dioxide-containingsteam, and, thus, to generate a lean liquid and thereby returns the leanliquid to the absorption tower, wherein the heat exchanger is placedbefore the flow divider, a portion of the first rich liquid is dividedbetween the absorption tower and the heat exchanger, the first carbondioxide release device heats the second rich liquid, using the leanliquid discharged from the regeneration tower as a heat source, thesecond carbon dioxide release device heats the third rich liquid and theportion of the first rich liquid, using the carbon dioxide-containingsteam discharged at the regeneration tower as a heat source, the heatexchanger heats the first rich liquid, using the lean liquid which haspassed through the first carbon dioxide release device as a heat source,and a flow rate of the portion of the first rich liquid and a flow rateof the third rich liquid are equivalent to each other.